It is common practice in offshore oil and gas production to have the wellhead and related casing hangers mounted at the ocean floor with the xmas tree and other production equipment mounted above the water level on a production platform. In such situations tieback conductors are used to connect the subsea wellhead equipment to the platform mounted production equipment. In a typical application the high pressure 183/4 inch casing head housing must be tied back to the production platform.
One example of a production tieback is shown in U.S. Pat. No. 4,343,495 wherein item 10 is a casing head housing which is tied back to a production platform by connector 14 and conductor 12. Connector 14 is joined to housing 10 by threaded engagement.
Another example of a tieback is disclosed in U.S. Pat. No. 3,497,243 wherein the conductor pipe 12 is threaded into wellhead housing 11.
Another tieback system is shown in U.S. Pat. No. 4,046,405 wherein the connections include threads, latching mechanisms and an axially threaded nut.